Treating photographic film



TREATING PHOTOGRAFHIC FILM Filed Sept. 26, 1930 gw'uemtoz Charles Hnlzwafih Patented Feb- 3, 193.4

1,947,160 TREATING PHOTOGRAPHIC FILM Charles Holzwarth, Parlin, N. J., assignor to Du Pont Film Manufacturing Corporation,

New York, N. Y., a corporation of Delaware Application September 26, 1930 Serial No. 484,643

1 Claim; (01. 91-69) This invention relates to the art of making I first take a film base preferably of cellulose photographic film base, and particularly to makacetate and preferably containing softening and ing film resistant to deformation or wrinkling. water-repelling agents, such as dibutyl phthalate ,Films of cellulosic material, such ascellulose or triphenyl phosphate. To both' sides of this 5 ester films, used in the manufacture of photofilm base I apply a nitrocellulose solution pre- 80 graphic materials, are hygroscopic and expand pared and applied as described herein. While when wet, particularly when being treated. this solution contains nitrocellulose as indicated, When dried after usual processing, they do not it does not contain a sufficient amount of any inuniformly assume their original smooth state but gredients to materially diminish the fire resisting have a tendency to retain areas presenting an properties of the finished film coated with my 65 irregular or wrinkled surface that is obviously solution. objectionable. This is referred to herein as the This solution may be applied by any well tendency to cockle. Films of cellulose acetate known apparatus, preferably immediately after possessthis tendency to an undesirable extent. the film base has been manufactured or cast,

The tendency to expand when wet is matebut care must be taken to make sure that the 70 rially reduced by adding softeners such as difilm ba e is thoroughly dried after it leaves the butyl phthalate, triphenyl phosphate, and such casting unit. My novelsolution is, of course,

substances that are inherently water repellent, applied to the film base prior to the application but in spite of this treatment, commercial film of any of the light sensitive emulsion coatings.

base approximately five to seven and one-half Only enough of my solution is applied to each 75 thousandths of an inch thick still remains un- ,side of the film base so that the coating resulting able to resist the tendency to cockle. therefrom will when finally dried thereon have This invention aims to provide a novel method a total thickness preferably not greater than of making film cockle-proof. Another object. of 6 the thickness of the film base used. Film my invention is to provide a novel method of base for motion picture use or for studio por- 80 treating a moisture resistant cellulose acetate trait use is made in thicknesses ranging from film so that it will remain in its original unlapproximately five to seven and one-half thouwrinkled state after being subjected to the vasandths of an inch. Therefore, such base when rious processes required in its subsequent manubearing on both sides thereof the herein defacture and commercial use. A further object scribed coating will have its total thickness in- 85 is to accomplish these ends without materially creased'not more'than 10%. I have found that diminishing any fire resistant properties of the this closely limits the nitrocellulose solution so film base used. Additional and more specific that it will not materially diminish the combusobjects will more clearly appear from the detion retarding properties of the fire resistant film tailed description herein presented. base used, or of the thus coated and finished 90 In the accompanying drawing, the figure diacockle-proof film. grammatically illustrates an enlarged cross -sec- A preferred and novel nitrocellulose solution tional view'of a cockle-proofed film comprising -a comprises the following: base of a fire resistant material, A, bearing 7 By wei 40 on both sides thereof a cellulose nitrate coating Ni ocellulose 5. 5 05 N. Ethyl alcohol (incorporated in the nitro- To enable those skilled in the art to use my ce lu ose) 2.00 invention I will as an illustration describe a precamphor 0. ferred method of carrying it into effect, with the Acetone 10. 00 45 understanding that modifications may be' made Butyl alcohol 10.00 and the invention embodied in different forms M0110 e hy t e y e glycol 0-00 without departing from its spirit and scope in Methanol (methyl alcohol) 61.45 its broader aspects. Castor oil. 0. 50'

' Inasmuch as theabove mentioned tendency I 50 to wrinkle or cockle is much less noticeable in Here they nitrocellulose furnishes the neces-- nitrate film than in acetate film, my improved sary body. Camphor and castor oil or the like method is therefore preferably applicable to fire can be used to add flexibility t0 the fi p odresistant cellulose acetate film or the like manuct. Castor oil or the like'while not essential ufactured either with or without the incorporaherein may also supply water-resisting quali- 55 tion of the above mentioned softening agents. ties.. Mono ethylether ethylene glycol or the like serves as an anti-clouding agent to prevent the water precipitation of the nitrocellulose during the final stages of drying. Methanol or the like is used as a solvent for the cellulose nitrate that will not affect the cellulose acetate. Acetone or the like is preferred herein as\an anchorage agent that will act upon the cellulose acetate. Butyl alcohol or the like acts as a preferred residual solvent. Ethyl alcohol is incorporated in commercial nitrocellulose and is incidental thereto. It is not essential herein.

What I claim as new and'desire to secure by Letters Patent is:

The method of cockle-prooflng photographic 

